Camel Milk Possible MERS-CoV Transmission Route

Scientists at the National Institute of Allergy and Infectious Diseases (NIAID) have observed in laboratory studies that Middle East respiratory syndrome coronavirus (MERS-CoV) remains stable for at least 72 hours in the unpasteurized milk of dromedary camels.

Previous research has found that camels carry MERS-CoV, which has caused at least 92 deaths out of 228 confirmed human cases, unpasteurized camel milk is consumed regularly by residents of the Arabian Peninsula, where the virus was first recognized in 2012. Researchers have not identified how the virus infects people, and the NIAID investigators are exploring whether milk may be a possible source of infection.

Contaminated milk products and direct contact with animal udders are known transmission routes of bacteria and other viruses. Thus far, however, MERS-CoV has not been detected in milk samples, nor do scientists know whether milk contaminated with the virus can infect people.

Previous studies by scientists from NIH’s National Institute of Allergy and Infectious Diseases (NIAID) have shown that MERS-CoV remains stable for up to 48 hours on different surfaces. In their current study, the NIAID investigators added an infectious dose of the virus to milk samples obtained from dromedary camels, goats and cows. The temperature of one sample set was maintained at 4° C, the other at 22° C. Samples from each set were immediately frozen at minus 80° C, and the others were frozen 8, 24, 48 and 72 hours after dilution.

The researchers found that virus concentration decreased the longer the sample was maintained before freezing, but less so in samples maintained at 4° C. In fact, they determined that camel and cow milk samples maintained at 4° C for 72 hours before freezing did not lose a significant amount of infectious MERS-CoV. Samples maintained at 22° C for 48 hours before freezing still contained infectious virus.

The group then repeated the virus concentration test on milk samples heat-treated for 30 minutes at 63° C and found no infectious virus, confirming that pasteurization might be an effective safety measure.

The NIAID investigators plan to further study camel milk to determine whether MERS-CoV is excreted into the milk of infected dromedary camels and, if so, whether handling or consuming contaminated milk is associated with MERS-CoV infection.